FYFD

Tag: fluid dynamics

  • Daily Fluids, Part 1

    Daily Fluids, Part 1

    Just getting cleaned up and ready for the day involves a lot of fluid physics. Here are a few of the phenomena you may see daily without realizing:

    Plateau-Rayleigh Instability
    This behavior is responsible for the dripping of your faucet. More specifically, it’s the reason that a falling jet breaks up into droplets. It works on rain, too!

    Forced Convection
    Everyone is familiar with a winter wind making them colder or hot air from a dryer getting the moisture off their hands. These are examples of forced convection – heat transfer by driving a fluid past a solid. Another common example? The fans in your computer!

    Liquid Atomization
    This is the process of breaking a liquid into lots of tiny droplets. Aside from any aerosol can ever, this phenomenon is also key to your daily shower and internal combustion in your car.

    Archimedes Principle
    This might be one of my favorite bits of the whole video because it hearkens back to some of my own earliest fluid dynamics exposure. Archimedes Principle says that buoyancy is equal to the weight of the fluid a body displaces. My mom (a science teacher) taught me about this one in the bathtub! It’s key to everything that ever floated, including us!

    Tune in all week for more examples of fluid dynamics in daily life. (Image credit: S. Reckinger et al., source)

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    A Day in the Life of a Fluid Dynamicist

    Today I’m sharing one of my favorite videos from last year’s Gallery of Fluid Motion. It’s a short film entitled “A Day in the Life of a Fluid Dynamicist.” Although some parts of it probably only apply to fluid dynamicists (Navier-Stokes equations, anyone?) a lot of the activities depicted are common to everyone. The film does a nice job of highlighting some of the many examples of fluid dynamics that we come across in our daily lives. As a film by scientists made for scientists, though, you may find some of the terminology obscure. Never fear! This week on FYFD, I’ll be breaking down some of the film’s segments, explaining what they mean, and showing you just how much fluid dynamics you experience every day! (Video credit: S. Reckinger et al.)

  • Vortices in the Wind

    Vortices in the Wind

    Heard Island, a remote patch of rock in the southwestern Indian Ocean, peeks its head above the marine cloud layer. The volcanic island disrupts the atmosphere enough to generate a von Karman vortex street, a line of alternating vortices shedding from either side of the island. Usually these vortices would march in a straight line downstream from their source. But here strong winds from the south have blown a bunch of its vortices northward, creating an unusual kink in the island’s wake. (Image credit: J. Schmaltz/LANCE EOSDIS Rapid Response; via NASA Earth Observatory)

  • Visualizing Smell

    Visualizing Smell

    Every day we’re surrounded by an invisible world of smells. Like the fluorescein dye in the animation above, these odors drift and swirl in the background flow. What you may not have stopped to consider when you smell the roses, though, is how the very act of sniffing changes the scent. When you inhale, filaments of the odor are drawn into your nose, and, likewise, when you exhale, your breathe mixes with the scent and sends it swirling outward in turbulent eddies. To see more about the science of scent, check out PBS News Hour’s full video below. (Video credit: PBS News Hour; GIF via skunkbear)

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    Paper Marbling

    Fluid dynamics and art have gone hand-in-hand for centuries. In this video, artist Garip Ay demonstrates one of the coolest fluids-based art techniques: paper marbling. In this technique, artists float ink or paints on a liquid surface, manipulate the colors as desired–in this case to recreate Van Gogh’s “Starry Night”–and then float a piece of paper atop the surface to transfer the image. Multiple cultures around the world developed marbling techniques, dating all the way back to the Middle Ages. Ay is an expert in ebru, a Turkish form of the art. For more of Ay’s art, check out his website and YouTube channel. (Video credit: G. Ay; via Gizmodo)

  • Bubble Tricks

    [original media no longer available]

    Everyone remembers playing with soap bubbles as a child, but most of us probably never became as adept with them as magician Denis Lock. In this video, Lock shows off some of the clever things one can do with surface tension and thin films. My favorite demo starts at 1:25, when he constructs a spinning vortex inside a bubble. He starts with one big bubble and adds a smaller, smoke-filled one beneath it. Then, using a straw, he blows off-center into the large bubble. This sets up some vorticity inside the bubble. When he breaks the film between the two bubbles, the smoke mixes into the already-swirling air in the larger bubble. Then he pokes a hole in the top of the bubble. Air starts rushing out the deflating bubble. As the air flows toward the center of the bubble, it spins faster because of the conservation of angular momentum and a miniature vortex takes shape.  (Video credit: D. Lock/Tonight at the London Palladium/ via J. Hertzberg)

  • Reader Question: Shower Curtains

    Reader Question: Shower Curtains

    Reader thansy asks:

    Why do the bottoms of shower curtains drift in toward the water coming from the shower head?

    We all know that moment. You’re minding your own business, scrubbing away, and all of a sudden, the shower curtain billows up and grabs you. Scientists have debated the cause of this behavior for years. Some argued that the curtain billowed due to hot air rising from the shower. Others claimed the fast-moving spray caused lift that pulled the curtain up. But fifteen years ago, one scientist tackled the problem computationally. He performed a numerical simulation of a shower head spraying into a bath and found that this spray of droplets creates a weak horizontal vortex in the shower.

    This shower vortex has a low-pressure core at the middle, which is thought to provide the suction that causes the shower curtain to billow. The scientist, David Schmidt, was awarded the 2001 Ig Nobel Prize for his work. (Image credits: N. Paix, D. Schmidt; research credit: D. Schmidt)

  • Swimming at Microscale

    Swimming at Microscale

    Tiny organisms live in a world dominated by viscosity. There’s no coasting or gliding. If a microorganism stops swimming, friction will bring it to a halt in less than the space of a hydrogen atom! To make matters worse, simply flapping an appendage forward and backward will get them nowhere. As we’ve seen before, these highly viscous laminar flows are reversible, meaning that a backward power stroke is simply undone by a mirrored forward recovery stroke. Instead, microorganisms like the paramecium swimming above are covered in tiny hairlike cilia which beat asymmetrically. They extend to their full length during the power stroke, but they stay bent during the forward recovery stroke. That asymmetry guarantees that they move more fluid backward than forward, thereby letting the paramecium make progress. (Image credit: C. Baroud, source)

  • Shelf Cloud

    Shelf Cloud

    Sydney, Australia was treated to a spectacular meteorological show over the weekend when an impressive shelf cloud swept over the city. These timelapses show the dramatic leading edge of the incoming thunderstorm. Notice how the cloud streams upward along the shelf. The storm is driven by this updraft of warm moist air, which rises until it is capped by the troposphere. At this point, the air spreads, creating an anvil-like shape, and cools. The moisture drawn up at the storm’s front will condense, freeze, and fall as rain or hail. When the updraft weakens, the storm will be dominated by the downdraft of the falling precipitation and eventually peter out. (Image credit: W. Reed and H. Vann, source; via J. Hertzberg)

  • Drawing Up Dew

    Drawing Up Dew

    Desert plants have evolved to efficiently collect and capture whatever water they can. Each leaf of the moss Syntrichia caninervis ends in a hairlike fiber called an awn (seen in white in the top image). Tiny as they are, awns are vital to the moss’s water collection, correlating to more than 20% of their dew collection. Extremely tiny grooves on the surface of the awn provide nucleation sites where dew condensed from fog collects. Once a droplet forms on the awn, it grows larger as more fog condenses (middle image). When the droplet grows large enough, the conical shape of the awn will cause surface tension to draw the droplets along the awn and toward the leaf (bottom image).

    (Credits: Syntrichia caninervis moss image – M. Lüth; videos and research – Z. Pan et al., Supplementary Videos 3 and 4; h/t to T. Truscott)